Links to the different topics

Introduction

This is my first model of a stripping shovel. Stripping shovels were used to remove the overburden in coal mines. This was done by digging a small stripe and fill another, already coaled out, with the overburden. That's why these shovels are called stripping shovels.The original of my model is a type 1050B and was built in 1941 by the Bucyrus Erie company. It was the successor of the type 950B.My model has all the features of the original - but in minifig scale. It is driven by ten motors, six old styled 9V, three new 9V, and one micromotor. Power comes from a 9V train transformer and is directed to the motors with the help of six pole reverser switches. If I should manage to tune the LEGO Dacta ControlLab Interface a bit, I will try to build a PC based control unit.

Crawler Undercarriage

The undercarriage of the shovel consists of four pairs of crawlers and the mounting of the turntable.Every pair of crawlers is driven by an old styled 9V motor. There's a power supply wire for each side of the undercarriage, but they are powered together. Therefore all crawlers have the same speed. Because of this and the fact that there's a steering mechanism, the speed of the crawlers in curves is not adjustable to the different radii. But this causes no problems because of the very slow speed of such machines.The steering mechanism is driven by a new 9V motor. Four gear racks act as 'hydraulic cylinders' and move the crawler pairs - the front ones are always parallel to each other and so are the rear ones.The crawler pairs feature a cardanic mounting to handle uneven terrain. This is supported by three rollers per crawler which are mounted in a movable frame.The weight of the undercarriage is 2.8 kg.

Turntable

The heavy weight of the upperstructure of 5.4 kg is supported by a heavy duty turntable. (By the way - the 2.8 kg of the undercarriage and the 5.4 kg of the upperstructure give a total weight of the model of 8.2 kg.)The turntable is built the same way, I describe in my Building Hints section under Heavy Duty Turntables. It has 32 rollers which lay on a flat ring on the undercarriage. Another ring lays on the rollers and is attached to the upper structure. A standard Technic turntable is used as king pin through which the electric wires transmit the power to the motors in the machine house. It is mounted upside down to mount the two 9V motors for the revolution in the upper structure - like in real.

Hoist Winch and Counterweight

In the time the Bucyrus Erie 1050B was built, several shovels had a feature which reduced the power rating of the main hoist motors. My model has the same feature - a counterweight for the bucket.This means that when the bucket goes up, a counterweight which is driven by the same winch goes down and vice versa. The momentum of the counterweight which acts on the winch is about the same as the one of the empty bucket. Therefore motor power is just needed to lift the payload.The counterweight goes up and down in the tower at the back end of the shovel. Because the tower is just half as high as the lifting height of the bucket, it has to be twice the weight of the bucket. In my model I used steel parts of about 300 g. Thanks to the counterweight, my model just needs one old styled 9V motor for the hoist winch.

Adjustable Stick

To vary the digging curve, the shovel has an adjustable stick. In real, the stick is cylindrical shaped to prevent it from being damaged, if there are side loads. I didn't manage to realize this with LEGO parts, therefore I built it in a special way just with plates. An advantage of this is the lightweight construction. Unfortunately this is compensated by the very heavy bucket.Adjustment works with the help of a winch with an endless cord. So the stick is always pulled in the desired direction.The cord goes over wedge belt wheels in the box shaped structures at the front end of the machine house and from there up to the mounting of the stick. There are another four wedge belt wheels - two on every side - which direct the cord to the front and the back end of the stick where it is fixed.

Bottom Dump Bucket

The shovel features a big bottom dump bucket with six teeth. It is mounted to the stick and is lifted with two cords.The bottom dump mechanism was the biggest problem to realize. Finally I found a solution which I think comes close to the one used in real. It works as follows: A lock which consists of a bolt which is hold in position with a rubber band holds the gate closed. A cord which is attached to the bolt and to a reel which itself is mounted to a micromotor is used to pull back the bolt. When doing so, the gate opens, driven by the gravity.To close the gate the bucket has to be lowered until the gate is in closed position again. Then the cord can be released by the micromotor and the bolt locks the gate.Because the bucket has to be lowered to do a new dig, it plays no matter that you can't close the gate in every position of the bucket and the stick.

It's in Minifig Scale

The model is built in minifig scale. This means a scale of about 1 / 40 to 1 / 45. Because I don't have blueprints of the original machine, the measurements are just about in the right dimension.Such a big machine has many different service points where the mechanics have to go to from time to time. Therefore all around the machine house are ladders and walkways. There is also lighting and floodlights to allow the machine to be operated at night.To get up to the operators cabin, a hinged ladder is mounted on the front right crawler pair. From there the operator has to climb three more ladders to finally reach the control levers in the cabin.More details include a small crane at the right side of the machine house which is used to lift up service equipment and spare parts. A welding equipment is located below a walkway beside the crane. The Bucyrus Erie logo is mounted on both sides above the machine house.All around the machine house are five (non openable) doors and a big sliding door. Through the open sliding door you can see details of the interior.